Dyspnea is a subjective sensation of difficult or uncomfortable breathing. The underlying neural pathways responsible for dyspnea are not well understood. Multiple interacting mechanisms are thought to be responsible for the sensation of dyspnea.
Chronic dyspnea is a challenging clinical entity and often frustrates both physicians and patients. We have found it useful to think of causes of dyspnea as belonging to the following categories:
- Pulmonary disease
- Cardiovascular disease
- Psychogenic disease
- Neuromuscular disease
A study done by Dr. R.S. Irwin and colleagues (Archives of Internal Medicine 1989; 100:1293-1299) reviewed 100 consecutive patients presenting with chronic dyspnea in an outpatient setting. 75% of the patients were found to have pulmonary disorders, 10% had cardiac disorders and psychogenic disorders, and deconditioning and gastroesophageal reflux disease each accounted for 5%. These authors found that specialized testing was often necessary, because the history and physical examination were often not sufficient to establish a diagnosis.
We have found the following approach to be most useful in assessing patients with unexplained dyspnea:
- A thorough history and physical are carried out with focused questioning on a description of the dyspnea with associated symptoms and any triggers that might be present.
- All patients should have a chest x-ray, pulmonary function tests, appropriate lab tests, and room air oxygen saturation.
- In selected patients, further testing may be necessary. We have found the most useful tests include methacholine challenge testing (MCT), cardiopulmonary exercise testing (CPET), ventilation perfusion scan, high resolution CT scan of the chest (HRCT chest), and echocardiography.